Google has spent more than $28 billion on a whopping 163 companies since 2001. That’s almost one company per month.

The search-engine-that-could has purchased all kinds of companies, services and technologies — from mapping companies to security services to gadgets and robots to gaming and facial recognition software and much, much, much more.

But with so many companies, we thought it’d be fun to look at the top 11 companies and services Google has acquired over the years, based on how they’ve impacted Google’s business.

Makani Power — Clean energy — $30 million

Google previously invested in the green energy startup before it completed its purchase of Makani Power last May. Since then, Makani has operated out of Google's X Labs to build airborne wind turbines, which have the potential to be the dominant form of clean energy. Google currently has a working prototype.

Titan Aerospace — Drone and UAVs — $60 million

Google has many uses for the New Mexico-based company that made solar-powered flying drones, which was purchased in April. Though it can contribute photos to Google Maps and Earth or even work with the Google X project Makani Power, Titan Aerospace is playing a big role in Google’s Project Loon, which strives to bring internet connectivity to those regions without it by beaming broadband from the sky.